The subject matter disclosed herein relates to storage tanks and, more specifically, to thief hatches for storage tanks.
Storage tanks, such as an above-ground or below-ground storage tank, may include openings designed to accept a venting device, such as a thief hatch, to provide access to the interior of the storage tank. For example, a thief hatch may provide a resealable opening through which a thief or other tool may be inserted into the interior of the storage tank.
As will be appreciated, the internal pressure (e.g., internal vapor pressure) of storage tanks may vary and may depend on various factors, such as the amount of fluid in the storage tank, the volatility of the fluid in the storage tank, temperature of the fluid in the storage tank, temperature outside the storage tank, thermal conductivity of the walls of the storage tank, and so forth. Accordingly, excessive vapor pressure in the storage tank may be relieved (e.g., in a controlled fashion). For example, a thief hatch may provide a seal that blocks fluid communication between the interior of the storage tank and the exterior of the storage tank when the vapor pressure within the tank is below a threshold and enables fluid communication between the interior of the storage tank and the exterior of the storage tank when the vapor pressure within the tank is above the threshold.